1. Field of the Invention
The present invention relates to a head-up display device mounted on a vehicle and particularly relates to a technique to notify a driver of a shift position of a transmission of the vehicle.
2. Description of the Related Art
An example of general head-up display devices mounted on vehicles is structured such that display light emitted from a projection unit is projected on an optical member (half mirror), which is called a combiner, and the light reflected by the surface of the combiner guided to a predetermined eye point, which is a driver's viewing position (e.g., refer to Japanese Patent Application Laid-open No. 2006-11122). The combiner is disposed at a position easily visible to the driver, such as above an instrument panel in front of a driver's seat. As the reflective surface of the display light, a front windshield is used instead of the combiner in some cases.
The head-up display device has an advantage in that a driver needs little focus adjustment to visually recognize a display image because the image is formed as a virtual image at a position in front of the position of the combiner in a traveling direction of the vehicle. The head-up display device allows the driver to visually recognize a scenery ahead of the vehicle visually recognized through the combiner and the display image formed ahead in the traveling direction of the vehicle in a superimposed manner, thereby making it possible to provide information in a new aspect different from a display using a typical display panel.
Such a head-up display device can be used for displaying a traveling speed of a vehicle, for example. The head-up display device is suitable for displaying high priority information such as a vehicle speed because the driver can visually recognize a speed indication while looking head-up, without significantly moving a sight line or adjusting the focus.
Gears (speed reduction ratios) of a transmission mounted on a vehicle are shifted in accordance with shift positions. For example, an automatic transmission has the following shift positions: a park position “P”, a reverse position “R”, a neutral position “N”, and a drive position “D”. A driver, thus, needs to grasp a current shift position when driving the vehicle. For example, if the driver starts driving the vehicle by changing the shift position to the reverse position “R” whereas the driver intends to drive the vehicle forward by changing the shift position to the drive position “D”, the vehicle may be moved in a different direction from that of the driver's intention.
The present invention has been made in view of the above-described circumstance, and it is an object of the present invention to provide a head-up display device that allows a driver to readily grasp the current shift position.